Hi Mar :)
honestly I think your sketches are looking really nice already for someone who's only been drawing for 4 months!
your lines are lacking confidence - being constructed of multiple tiny lines rather than one flowing one. Don't be afraid to make mistakes, this is why we practice. You can also use varying line thickness to hint towards shadows and thus volumes. I see you using the line of action in some sketches which is great and an amazing tool to get the general direction of the gesture right. Try working in some volumes into your figures by taking more time than just a minute when you find a reference you particularly like. I also think maybe you could try working on a sketch until the entire figure is drawn and all limbs are recognizable beyond just lines! And as always, keep your eyes on the reference more than the paper.
these are just some tips I think might help you get, at least, different results and then eventually drawings you are satisfied with
keep going! you are doing so well. I wish you all the best :)
